The research described in this proposal is an attempt to neuroanatomically localize the brain mechanisms responsible for the memory retrieval phenomenon called state-dependent learning. This term refers to the fact that a behavioral response learned while an animal is drugged may thereafter be optimally performed only when the animal is again drugged; hence, the drug condition during acquisition determines the drug state that will allow optimal subsequent performance. The term "drug discrimination" refers to a closely related phenomenon; animals can easily be trained to perform one response when drugged and a different response when undrugged. Both of these phenomena are also produced by several nonpharmacological manipulations. Their cause is unknown. although they have been primarily studied with drugs, interest in these phenomena derives primarily from the fact that they apparently reflect an important property of the brain mechanisms involved in learning and retention. In the proposed research, drugs and electrical stimulation will be bilaterally applied to individual brain structures in rats. The degree of state-dependent learning produced by these manipulations will be determined by training rats to discriminate their presence or absence in a 2-bar discriminative operant task. It is expected that micro-injection or stimulation in many brain structures will be relatively nondiscriminable, but that at some sites rapid discriminative control will develop. The present experiments are aimed at determining which brain structures are critically involved in the state-dependancy phenomenon. It is reasoned that such experiments might provide an improved basis for theory evaluation and for future research on the mechanism for state-dependency.